Laser printers and photocopier machines have traditionally used a dry-powder toner for electrostatically developing a visible image on a sheet of paper. However, in liquid electrophotography (LEP), a visible image is developed by electrostatic toners containing pigment components dispersed in an insulating carrier liquid. LEP is known to be used to produce multi-color images with liquid toners.
Given the ever increasing demand for improved printing capabilities, it is desirable to have printers and copiers that are capable of providing increased output from a toner cartridge containing the toner medium. Specifically, a toner cartridge which is capable of producing many more printed pages relative to what the typical toner cartridge produces is highly desirable.
One method of accomplishing the goal of increasing the output of an LEP toner cartridge is to use a toner concentrate. When a toner concentrate is mixed with a carrier fluid in appropriate amounts, output capabilities are increased while the dimensions of the cartridge containing the toner are decreased. Accordingly, a smaller cartridge can be used with a toner concentrate to produce output equivalent with that of traditional toner cartridges.
The problems that plague the use of toner, and especially toner concentrate, include the fact that toner is extremely messy if not properly confined. Furthermore, when using concentrate, the relatively high ratio of pigment particles in the carrier fluid creates a thicker, more pasty mixture which becomes more difficult to remove or pump out of the cartridge. Moreover, when mixing an LEP toner concentrate with a carrier fluid, exact, metered amounts must be mixed to produce appropriate ratios of pigment particles in the carrier fluid to avoid flow and image problems associated with the electrophotographic process and incorrect mixture ratios.
Given the continuous effort in the computing and printing industries to increase output, shrink dimensions, and create simpler, easier to use, and cheaper products, the foregoing problems associated with using LEP toner concentrate present challenges to be overcome. Accordingly, objects of the present invention are to provide an improved cartridge for dispensing LEP toner concentrate with precise metering capabilities for mixing the concentrate with a carrier fluid. Further objects are to provide a cartridge that is easy to use, mechanically simple, inexpensive, and leak-free.